The present invention relates to a technique of cleaning a substrate (a wafer) in semiconductor device fabrication or the like.
Semiconductor devices for use in networks or digital household electric appliances are desired to be further sophisticated, multifunctional, and low in power consumption. Accordingly, the trend toward micro-patterning for circuits has been developed. As the development of micro-patterning proceeds, a pattern collapse of the circuits has been becoming controversial. In semiconductor device fabrication, cleaning steps for the purpose of removing particles and metallic impurities are frequently employed, which results in a 30-40% occupation of the whole of a semiconductor fabrication process by the cleaning step. If the aspect ratio of the pattern is increased with the trend toward micro-patterning of the semiconductor devices, the pattern is to collapse when a gas-liquid interface passes through the pattern after cleaning or rinsing. This phenomenon is a pattern collapse.
In Patent Publication 1, there is disclosed a technique of changing a cleaning liquid from water to 2-propanol before a gas-liquid interface passes through a pattern, as a method for suppressing the pattern collapse. However, it is said that there are some limitations, for example, a limitation that an aspect ratio of a pattern adaptable thereto is not higher than 5.
Additionally, in Patent Publication 2, there is disclosed a technique directed toward a resist pattern, as a method for suppressing the pattern collapse. This is a method of suppressing the pattern collapse by decreasing a capillary force as much as possible.
However, the technique disclosed as above is directed toward the resist pattern and is for reforming a resist itself. Moreover, a treatment agent can finally be removed together with the resist, so that it is not necessary to estimate a process of removing it after drying; therefore, this technique cannot be applied to the present object.
Furthermore, Patent Publication 3 discloses a cleaning process for preventing the pattern collapse, in which surface-reforming by oxidation or the like is conducted on a wafer surface provided to have an uneven pattern by a film containing silicon and a water repellent film is formed on the surface by using a water-soluble surfactant or a silane coupling agent to reduce the capillary force.
Additionally, in Patent Publications 4 and 5, there is disclosed a technique of preventing the pattern collapse by performing a hydrophobicity-providing treatment with use of a treatment liquid containing a silylation agent (represented by N,N-dimethylaminotrimethylsilane) and a solvent.